macOS: workaround a dyld/libunwind deadlock issue since 12.1

[vtjnash]

Apple reintroduced the old bug that we previously worked around in
fad04d3 with a similar patch to this.

Fixes #43578

[staticfloat]

Is there a minimal reproducer that I can send to Apple?

[vtjnash]

You can potentially just note that the documentation for these functions in libunwind implies it doesn't acquire a lock, and that dyld is now violating that: http://www.nongnu.org/libunwind/man/unw_step(3).html#section_4

[staticfloat]

Alright, I opened a feedback with Apple, we'll see if it goes anywhere.

[IanButterworth]

I can confirm that the MWE from #43578 is fixed

julia> @profile while true
          run(`pwd`)
       end
/Users/ian/Documents/GitHub/julia
/Users/ian/Documents/GitHub/julia
/Users/ian/Documents/GitHub/julia
etc.

but stress testing it here made it deadlock with ^C and ^T not working

% JULIA_DEPOT_PATH=/tmp/5454 ./julia
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.8.0-DEV.1248 (2022-01-07)
 _/ |\__'_|_|_|\__'_|  |  jn/43578/a51e2d83c0 (fork: 1 commits, 0 days)
|__/                   |

julia> using Pkg, Profile

julia> @profile Pkg.add("PNGFiles")
  Installing known registries into `/tmp/5454`
    Updating registry at `/tmp/5454/registries/General.toml`
   Resolving package versions...

[vtjnash]

with ^C and ^T not working

Good catch. That is a different (but closely related) bug.

[IanButterworth]

Unfortunately something's still deadlocking for me. This is stopped with 0% cpu.

julia> @profile Pkg.add("PNGFiles")
   Resolving package versions...
  No Changes to `~/.julia/environments/v1.8/Project.toml`
  No Changes to `~/.julia/environments/v1.8/Manifest.toml`
Precompiling project...
  Progress [===>                                     ]  12/191
  ◑ SentinelArrays
  ✓ Calculus
  ✓ RoundingIntegers
  ◑ StaticArrays
  ✓ AbstractFFTs
  ✓ IndirectArrays
  ✓ ExprTools
  ✓ IteratorInterfaceExtensions
  ✓ TensorCore
  ✓ StatsAPI
  ✓ CEnum
  ◓ FixedPointNumbers
  ◓ FillArrays
  ✓ OpenLibm_jll
  ✓ InverseFunctions
  ◑ WoodburyMatrices
  ✓ CompilerSupportLibraries_jll
  ◐ MacroTools
  ◒ Preferences
  ◒ Parsers
  ◑ Compat
  ◑ Observables
  ◓ Requires
  ◒ DataValueInterfaces
  ◓ RealDot

[IanButterworth]

I've tried, but I can't get this to deadlock! Thanks @vtjnash !

[IanButterworth]

I just hit a similar repeatable deadlock on ubuntu on master

julia> import Pkg

julia> Pkg.update()
    Updating registry at `~/.julia/registries/PrivateRegistry`
    Updating git-repo `git@github.com:PrivateOrg/PrivateRegistry`
    Updating registry at `~/.julia/registries/General.toml`
  No Changes to `~/.julia/environments/v1.8/Project.toml`
  No Changes to `~/.julia/environments/v1.8/Manifest.toml`
        Info Some packages have new versions but cannot be upgraded. To see why use `status --outdated`

julia> using Profile

julia> @profile Pkg.update()
    Updating registry at `~/.julia/registries/PrivateRegistry`
    Updating git-repo `git@github.com:PrivateOrg/PrivateRegistry`
    Updating registry at `~/.julia/registries/General.toml`
┌ Error: Some registries failed to update:
│     — /home/ian/.julia/registries/PrivateRegistry — failed to fetch from repo
└ @ Pkg.Registry ~/Documents/GitHub/julia/usr/share/julia/stdlib/v1.8/Pkg/src/Registry/Registry.jl:446
  No Changes to `~/.julia/environments/v1.8/Project.toml`
  No Changes to `~/.julia/environments/v1.8/Manifest.toml`
^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C

Note that PrivateRegistry is the only registry added via ssh

I added a debug print to that error throw

Error: Pkg.Types.PkgError("failed to fetch from git@github.com:PrivateOrg/PrivateRegistry, 
error: GitError(Code:ERROR, Class:SSH, Failed to retrieve list of SSH authentication 
methods: Error waiting on socket)"

[KristofferC]

This requires a manual backport against backports-release-1.6.